Which statement is true about chemical reactions at equilibrium?
The forward and backward reactions proceed at equal rates
The forward and backward reactions have stopped
The concentrations of the reactants and products are equal
The forward reaction is exothermic
Chemical equilibrium is referred to as dynamic because, at equilibrium, the...
equilibrium constant changes
reactants and products keep reacting
rates of the forward and backward reactions change
concentrations of the reactants and products continue to change
What is the equilibrium expression for the reaction: N2 + 3H2 --> 2NH3 (all in the gaseous state)?
For a reaction which goes to completion, the equilibrium constant, Kc, is:
more than 1 (Kc >>1)
less than 1 (Kc
The equilibrium constant for the reaction below is 1.0 x 10^-14 at 25oC and 2.1 x 10^-14 at 35oC. What can be concluded from this information?
2H2O (l) H3O+ (aq) + OH- (aq)
The ionization of water is endothermic
[H3O+] decreases as the temperature is raised
Water is a stronger electrolyte at 25oC
[H3O+] is greater than [OH+] at 35oC
Ethanol is manufactured from ethene using the reaction:
C2H4 + H2O C2H5OH (Delta-H = -46 KJ)
Which conditions favour the highest yield of ethanol?
High pressure and low temperature
High pressure and high temperature
Low pressure and low temperature
Low pressure and high temperature
N2O4 and NO2 produce an equilibrium mixture according to the equation:
N2O4 2NO2 (Delta-H = 57.2 KJ/mol)
An increase in the equilibrium concentration of NO2 can be produced by increasing which of the factors below?
1) Pressure 2) Temperature
both 1 and 2
neither 1 or 2
Which changes will increase the amount of SO3 (g) at equilibrium?
2SO2 + O2 2SO3 (Delta-H = -197KJ)
1) increasing temperature 2) decreasing volume 3) adding a catalyst
1 and 3 only
1, 2 and 3
For the reaction N2 + 3H2 2NH3 (Delta-H = -92 KJ)
What conditions will produce the highest percentage of NH3 at equilibrium?
Low pressure and low temperature
Hydrogen and iodine react in a closed vessel to form hydrogen iodide.
H2 + I2 2HI
at 350oC, Kc = 60
at 445oC, Kc = 47
Increased temperature as the forward reaction is exothermic, and increased pressure as there are two gaseous reactants and only one gaseous product
Increased temperature as the forward reaction is endothermic, and pressure has no effect as there are equal amounts, in mol, of gaseous reactants and products
Decreased temperature as the forward reaction is exothermic, and decreased pressure as there are 2 moles of gaseous product but only 1 mole of each gaseous reactant
Decreased temperature as the forward reaction is exothermic, and pressure has no effect as there are equal amounts, in mol, of gaseous reactants and products
An increase in temperature increases the amount of chlorine present in the following equilibrium.
PCL5 (s) PCL3 (l) + CL2 (g)
What is the best explanation for this?
The higher temperature increases the rate of the forward reaction only.
The higher temperature increases the rate of the reverse reaction only
The higher temperature increases the rate of both reactions but the reverse reaction is affected more than the forward
The higher temperature increases the rate of both reactions but the forward reaction is affected more than the reverse
The reaction between sulfur dioxide and oxygen (the contact process) occurs according to the equation below: 2SO2 + O2 2SO3 (Delta-H = -197)
A higher equilibrium concentration of SO3 will be produced by all of the following changes in a reaction conditions except...
adding more O2
adding a catalyst
decreasing the temperature
The reaction between methane and hydrogen sulfide is represented by the equation below:
CH4 + 2H2S CS2 + 4H2
What is the equilibrium expression for this reaction?
[CS2] 4[H2]/[CH4] + 2[H2S]
At 35oC, Kc = 1.6 x 10^-5 mol/dm^3 for the reaction:
2NOCL 2NO + Cl2
Which relationship must be correct at equilibrium?
[NO] = [NOCl]
2[NO] = [Cl2]